Role of altholactone in inducing type II apoptosis signalling pathway and expression of cancer-related genes in cervical carcinoma HeLa cell line

Inhibition of topoisomerase IIα and induction of DNA damage in cholangiocarcinoma cells by altholactone and its halogenated benzoate derivatives

Topoisomerase IIα enzyme (Topo IIα) plays a critical function in DNA replication process and is considered to be a promising target of anti-cancer drugs. In the present study, we reported that the altholactone derivatives modified by adding a halogenated benzoate group showed greater inhibitory activity on Topo IIα enzyme in cell-free system concomitant with cytotoxicity against the CCA cell lines (KKU-M055 and KKU-M213) than those of the parent altholactone. However, the cytotoxic activities of four halogenated benzoate altholactone derivatives including iodo-, fluoro-, chloro-, and bromobenzoate derivatives (compound 1, 2, 3, and 4, respectively) were of equal potency. The fluorobenzoate derivative (compound 2) was chosen for investigating the underlying mechanism in CCA cells. Compound 2 arrested CCA cell cycle at sub G1 phase and induced apoptotic cell death. It markedly inhibited Topo IIα protein expression in both KKU-M055 and KKU-M213 cells, which was accompanied by DNA double-strand breaks demonstrated by an increase in phosphorylated H2A.X protein. Interestingly, KKU-M055 cells, which express higher Topo IIα mRNA compared to KKU-M213 cells, showed greater sensitivity to the compound, indicating the selectivity of the compound to Topo IIα enzyme. By computational docking analysis, the binding affinity of altholactone (-52.5 kcal/mol) and compound 2 (-56.7 kcal/mol) were similar to that of the Topo II poison salvicine (-53.7 kcal/mol). The aromatic moiety of both altholactones embedded in a hydrophobic pocket of Topo II ATPase domain. In addition, compound 2 induced the formation of linear DNA in Topo II-mediated cleavage assay. Collectively, our results demonstrate that the addition of fluorobenzoyl group to altholactone enhances potency and selectivity to inhibit type IIα topoisomerases. Atholactone and fluorobenzoate derivative act as Topo II cleavage complexes stabilizing compounds or Topo II poisons preferentially through binding at ATPase domain of Topo IIα, leading to DNA double-strand breaks and apoptosis induction. Such activity of 3-fluorobenzoate derivative of altholactone should be further explored for the development of an anti-cancer drug for CCA.

Caspase-8 Induces Lysosome-Associated Cell Death in Cancer Cells

Caspase-8, a well-characterized initiator of apoptosis, has also been found to play non-apoptotic roles in cells. In this study, we reveal that caspase-8 can induce cell death in a special way, which does not depend on activation of caspases and mitochondrial initiation. Instead, we prove that caspase-8 can cause lysosomal deacidification and thus lysosomal membrane permeabilization. V-ATPase is a multi-subunit proton pump that acidifies the lumen of lysosome. Our results demonstrate that caspase-8 can bind to the V₀ domain of lysosomal Vacuolar H⁺-ATPase (V-ATPase), but not the V₁ domain, to block the assembly of functional V-ATPase and alkalinize lysosomes. We further demonstrate that the C-terminal of caspase-8 is mainly responsible for the interaction with V-ATPase and can suffice to inhibit survival of cancer cells. Interestingly, regardless of the protein level, it is the expression rate of caspase-8 that is the major cause of cell death. Taken together, we identify a previously unrevealed caspase-8-mediated cell death pathway different form typical apoptosis, which could render caspase-8 a particular physiological function and may be potentially applied in treatments for apoptosis-resistant cancers.

Goniothalamin-Related Styryl Lactones: Isolation, Synthesis, Biological Activity and Mode of Action

This review covers the chemistry and biological aspects of goniothalamin-related styryl lactones isolated from natural sources. This family of secondary metabolites has been reported to display diverse uses in folk medicine, but only a limited number of these compounds have been throughly investigated regarding their biological profile. Herein, we cover the goniothalamin-related styryl lactones having a C6-C3-C4 framework which appeared in the literature for the first time in the period 2000-2017, and the reports on the synthesis, biological activity and mechanism of action which were published from 2007-2017.

Application of sesquiterpene lactone: A new promising way for cancer therapy based on anticancer activity

Cancer is one of the most dangerous diseases that are rapidly increasing globally. After heart disease, it is the second leading cause of death, accounting for seven million deaths each year. Chemotherapy is the use of cytotoxic drugs on cancer cells. But the use of common chemotherapy drugs poses a problem due their high side effects and low efficacy. As a result, efforts are on to find new potent compounds with low side effects. The compounds extracted from plants have been studied in this regard due to their prevalence. Sesquiterpene lactones are a group of natural compounds that were first detected in Asteraceae dark plants. These compounds exercise their effects by reacting with functional groups available on proteins and enzymes, especially the thiol group. Owing to the high side effects as an antitumor synthetic drugs, efforts are being made to find drugs with high efficiency and low side effects. Their high structural ranges have attracted the attention of many researchers as a potential source of new anticancer drugs.

Altholactone Inhibits NF-κB and STAT3 Activation and Induces Reactive Oxygen Species-Mediated Apoptosis in Prostate Cancer DU145 Cells

Altholactone, a natural compound isolated from Goniothalamus spp., has demonstrated anti-inflammatory and anticancer activities, but its molecular mechanisms are still not fully defined. Nuclear factor kappa B (NF-κB) and signal transducer and activator of transcription 3 (STAT3) play pivotal roles in the cell survival of many human tumors. The objective of this study was to elucidate the mechanism of action of altholactone against prostate cancer DU145 cells and to evaluate whether its effects are mediated by inhibition of NF-κB and STAT3 activity. Altholactone inhibited proliferation of DU145 cells and induced cell cycle arrest in S phase and triggered apoptosis. Reporter assays revealed that altholactone repressed p65- and TNF-α-enhanced NF-κB transcriptional activity and also inhibited both constitutive and IL-6-induced transcriptional activity of STAT3. Consistent with this, altholactone down-regulated phosphorylation of STAT3 and moreover, decreased constitutively active mutant of STAT3 (STAT3C)-induced transcriptional activity. Altholactone treatment also results in down-regulation of STAT3 target genes such as survivin, and Bcl-2 followed by up regulation of pro-apoptotic Bax protein. However, pre-treatment with the antioxidant N-acetylcysteine (NAC) significantly inhibited the activation of Bax and prevented down-regulation of STAT3 target genes. Collectively, our findings suggest that altholactone induces DU145 cells death through inhibition of NF-κB and STAT3 activity.